Homogenizing heterogeneous foils for light alloy metal parts

ABSTRACT

A method for the manufacturing of an object. The method includes receiving a desired alloy composition for the object, depositing a plurality of foils in a stack to form the object, applying heat to the stack at a first temperature to bond the plurality of foils to each other, and applying heat to the stack at a second temperature to homogenize the composition of the stack. The homogenized stack has the desired alloy composition.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International (PCT) PatentApplication No. PCT/US2021/065196, filed internationally on Dec. 27,2021, and claims the benefit of and priority to U.S. provisionalapplications Nos. 63/131,285 and 63/257,091, filed on Dec. 28, 2020, andOct. 18, 2021, respectively, and International (PCT) Patent ApplicationsNos. PCT/US2021/030879 and PCT/US2021/036770, filed internationally onMay 5, 2021, and Jun. 10, 2021, respectively, the entire disclosure ofeach of which is hereby incorporated by reference as if set forth intheir entirety herein.

TECHNICAL FIELD

Embodiments described herein relate to methods and systems forfabricating an object and, more particularly but not exclusively, tomethods and systems for manufacturing objects having a desired alloycomposition from stacks of foils having compositions that differ fromthe desired alloy composition.

BACKGROUND

Laminated object manufacturing (LOM) techniques generally involvestacking multiple foils consisting of layers of at least two alloys andbonding the foils together to yield a solid object. Parts assembled viacustomary LOM techniques have different compositions in bonded regionsbetween foils and in structural parts of foils, alternating throughoutthe bulk of the part. These composition gradients throughout the partmay cause the mechanical properties of the composite LOM-assembled partsto not equal the properties predicted by the average composition of thealloy.

A need therefore exists for improved LOM techniques.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription section. This summary is not intended to identify or excludekey features or essential features of the claimed subject matter, nor isit intended to be used as an aid in determining the scope of the claimedsubject matter.

According to one aspect, embodiments relate to a method for themanufacturing of an object. The method includes receiving a desiredalloy composition for the object; depositing a plurality of foils in astack to form the object; applying heat to the stack at a firsttemperature to bond the plurality of foils to each other; and applyingheat to the stack at a second temperature to homogenize the compositionof the stack, wherein the homogenized stack has the desired alloycomposition.

In some embodiments, the plurality of foils are patterned.

In some embodiments, the plurality of foils comprises foils having atleast two different compositions.

In some embodiments, each foil comprises a plurality of layers. In someembodiments, each layer comprises an aluminum alloy, a magnesium alloy,or a titanium alloy. In some embodiments, the alloying material isaluminum, chromium, copper, lithium, magnesium, titanium, nickel,silicon, or zinc. In some embodiments, a first layer forms a core of thefoil and a second layer forms a cladding of the foil.

In some embodiments, each foil is between 25 and 1000 micrometers inthickness.

In some embodiments, the second temperature is less than the meltingpoints of the plurality of foils.

In some embodiments, the second temperature is approximately or lessthan the solidus temperature of the plurality of foils of the desiredalloy composition.

In some embodiments, the first temperature and the second temperatureare the same.

In some embodiments, the application of heat at the first temperatureoccurs in a first processing unit and the application of heat at thesecond temperature occurs in a second processing unit. In someembodiments, the stack is maintained at the first temperature duringtransfer from the first processing unit to the second processing unit.

In some embodiments, the method further includes quenching the stackafter homogenization. In some embodiments, the quenching occurs in thesame processing unit used for homogenizing the stack.

In some embodiments, the desired alloy composition is a homogenouscomposition that is non-identical to that of the plurality of foils.

BRIEF DESCRIPTION OF DRAWINGS

Non-limiting and non-exhaustive embodiments of this disclosure aredescribed with reference to the following figures, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified.

FIG. 1 depicts a side view cross section of a metal laminated objectmanufactured in accordance with one embodiment;

FIG. 2 depicts trimetric and object views of the metal laminated objectof FIG. 1 in accordance with one embodiment;

FIG. 3 depicts cross sections of individual foils in accordance with oneembodiment;

FIGS. 4A-D illustrate foils in various configurations in accordance withmultiple embodiments;

FIG. 5 illustrates a concentration profile of an interface between aninterlayer and two core layers in accordance with one embodiment;

FIG. 6 illustrates an operating profile of a homogenization process inaccordance with one embodiment;

FIG. 7 depicts a flowchart of a method for the manufacturing of anobject in accordance with one embodiment;

FIG. 8 depicts an additive manufacturing system comprising two platesconfigured to apply at least one of heat and pressure to layer stack tojoin layers in the layer stack in accordance with one embodiment;

FIG. 9 schematically shows a method for the additive manufacturing of anobject through diffusion bonding in accordance with one embodiment;

FIG. 10 schematically shows a method for the additive manufacturing ofan object through transient liquid phase (TLP) diffusion bonding inaccordance with one embodiment;

FIG. 11 schematically shows a method for the additive manufacturing ofan object through brazing in accordance with one embodiment; and

DETAILED DESCRIPTION

Various embodiments are described more fully below with reference to theaccompanying drawings, which form a part hereof, and which show specificexemplary embodiments. However, the concepts of the present disclosuremay be implemented in many different forms and should not be construedas limited to the embodiments set forth herein; rather, theseembodiments are provided as part of a thorough and complete disclosure,to fully convey the scope of the concepts, techniques andimplementations of the present disclosure to those skilled in the art.Embodiments may be practiced as methods, systems or devices.Accordingly, embodiments may take the form of a hardware implementation,an entirely software implementation or an implementation combiningsoftware and hardware aspects. The following detailed description is,therefore, not to be taken in a limiting sense.

Reference in the specification to “one embodiment” or to “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiments is included in at least one exampleimplementation or technique in accordance with the present disclosure.The appearances of the phrase “in one embodiment” in various places inthe specification are not necessarily all referring to the sameembodiment.

In addition, the language used in the specification has been principallyselected for readability and instructional purposes and may not havebeen selected to delineate or circumscribe the disclosed subject matter.Accordingly, the present disclosure is intended to be illustrative, andnot limiting, of the scope of the concepts discussed herein.

Embodiments of the present invention include methods used to homogenizethe composition of light alloy laminated parts. These laminated partsmay be the product of a LOM process. In some embodiments, the parts maycomprise multiple foils bonded together through some method, with eachfoil comprising at least one core layer and at least one interlayer. Inother embodiments, the parts may comprise multiple foils bonded togetherthrough some method, with alternating foils of a uniform core layer anda uniform interlayer. The process consists of applying heat for apredetermined processing time to promote solid-state diffusion of thealloying elements throughout the bulk of the part in some embodiments.Solid-state diffusion homogenizes the composition of alloying elementsthroughout the bulk of the part in order to improve the mechanicalproperties of the LOM-produced parts in some embodiments. In embodimentsof this method, no appreciable quantity of material is added to thepart.

In some embodiments, both the compositions and relative fractions of thecomponent layers that make up the foils are selected so that the fullyhomogenized part has an average composition that corresponds to a targetalloy. Two or more layers of different alloys that are combined andhomogenized using this method may produce a third alloy that isdetermined by the composition and thicknesses of the component layers.In some embodiments, the target alloy has composition and materialproperties similar to a commonly manufactured, commercially-availablealuminum alloy.

The term “foil” refers to the metallic sheet used to form each layer ina layer stack. The foil may comprise one or more sub-layers, of whichthere is at least one layer, and optionally some number of interlayerscomprising a different metal alloy from the first layer. In someembodiments, a foil has a thickness in one dimension between 10 μm and10 mm. In some embodiments, a foil has a thickness in one dimensionbetween 25 μm and 1000 μm. In further embodiments, a foil may have athickness in one dimension between 50 μm and 500 μm. In someembodiments, the foil may be patterned corresponding to the design ofthe object(s) and its support structure(s). In some embodiments, thefoil may comprise at least one of Al, Sb, Ba, Be, Bi, B, Cd, Ca, C, Cr,Co, Cu, Gd, Ga, H, Fe, Pb, Li, Mg, Mn, Mo, Nd, Ni, Nb, N, O, Pd, P, K,S, Si, Ag, Na, Sr, S, Ta, Th, Sn, Ti, V, Y, Zn, Zr, or a rare earthmetal. In some embodiments, the foil may comprise at least one ofaluminum, magnesium, titanium, aluminum alloy, magnesium alloy, ortitanium alloy.

The terms “core” or “core layer” refer to a foil or a portion of a foilthat comprises the majority of a layer stack. The composition of thealloy used for the core layer material is described in terms of theprimary alloying elements.

The term “interlayer” refers to the foil or the portion of the foil thatallows adjacent foils to bond. In some embodiments, the interlayer maybe on the outside of the foil, applied to at least one face of a corelayer. In some embodiments, the thickness of the interlayer is less thanthe thickness of the core layer. The composition of the alloy used forthe interlayer is described in terms of the primary alloying elements.

The terms “clad layer” or “cladding” refer to an interlayer materialbonded to a core layer prior to the start of the bonding andhomogenization process. In some embodiments, a thin interlayer of onecomposition roll bonded to a core layer would be described as a “cladfoil.”

A “layer stack” refers to at least two foils. A single foil may includeat least one support region and at least one object region in someembodiments. “Support” refers to the non-object component of the foilthat, when bonded together, forms a holder or jig that conforms to theobject exterior and may be used in subsequent post-processing. Thisholder or jig, formed as a combination of multiple support regions, maybe referred to as a “support section.” The combination of object regionsmay be referred to as an “object section.” The process of combining maybe referred to as “joining.”

The term “aluminum” refers to any material that comprises aluminum. Forexample, a material comprising aluminum may refer to a material of puremolecular aluminum, aluminum that is pure to a standard industrialgrade, an alloy of aluminum and at least one other element, or anycombination thereof. In the case where an alloy comprises a specificmetal such as aluminum, at least the plurality of the alloy compositionis the same specific metal. The secondary alloying elements present maybe subsequently described.

Some embodiments herein relate to methods to manufacture metal objectsfrom constituent metal layers with comparable mechanical properties. Insome embodiments, these methods avoid the use of adhesives betweenlayers and instead use high-strength metallic bonds between theconstituent layers to form an object. For aluminum parts, someembodiments may use bonding methods such as diffusion bonding, transientliquid phase diffusion bonding, and/or brazing. Specific configurationsof materials, such as alloy composition, alloy structure includingcomposites of two or more sub-layers with distinct compositions, andprocess conditions, such as applied temperature and pressure, may yieldstrong metallic bonds with shorter and more robust processes useful formanufacturing aluminum parts.

In some embodiments, manufacturing methods described herein firstreceive a desired alloy composition for an object. These embodimentsthen apply heat to a stack of foils comprising at least one core layerand at least one interlayer to homogenize the composition of the stack.The resultant product is a homogenized object that has the desired alloycomposition. The foils in the stack may be selected so that, e.g., onelayer has a surplus of one element and an adjacent layer has adeficiency of the same element so that the resulting object has adesired proportion of the element. This may be true of a plurality ofelements forming a desired composition for an object.

FIG. 1 depicts a side view cross section of a metal laminated object 100manufactured in accordance with one embodiment. In some embodiments, theobject 100 may be manufactured on a print bed 105. In some embodiments,a foil 110 may be deposited onto the print bed 105. In some embodiments,multiple foils may be deposited either directly onto the first foil 110or may be later added on top of the first foil 110.

FIG. 2 depicts trimetric 205 and object 210 views of the metal laminatedobject of FIG. 1 in accordance with one embodiment. The object may beenclosed in support sections 215, 220 and, as explained in furtherdetail below, those support sections 215, 220 may be removed after theobject section 225 is formed to finalize the metal laminated object.

FIG. 3 depicts cross sections of individual foils 305, 315, 325 inaccordance with one embodiment. In some embodiments, at least one foilin a stack of foils (not shown) may be comprised exclusively of a corelayer 310. In some embodiments, a foil 315 may comprise a core layer 330and a separate interlayer 335 on one surface. In some embodiments, theinterlayer 335 may be on top of the core layer 330. In some embodiments,the interlayer 335 may be on the bottom of the core layer 330. In someembodiments, a foil 325 may comprise a core layer 350 and twointerlayers 335 on either side of the foil.

In some embodiments, the core layer may comprise aluminum. In someembodiments, the core layer may be an aluminum alloy.

In some embodiments, the interlayer may comprise a metal or alloy havinga lower melting point than the core layer. In some embodiments, theinterlayer material may comprise at least one of aluminum, copper,chromium, iron, magnesium, manganese, silicon, titanium, and zinc. Insome embodiments, the metallic elements may be present in a number ofdifferent combinations, each composition selected for a particular setof properties that matches its bonding method, such as surface oxideresistance, surface oxide disruption, optimal melting temperatures, andthe properties of the liquid state such as wettability over the corelayer. In some embodiments, the two interlayers may comprise differentmaterials. In some embodiments, the two interlayers may be identical.

In some embodiments, the thickness for the interlayer may be 1-50% ofthe thickness of the core layer. In some embodiments, the thickness forthe interlayer may be 0-5% of the thickness of the core layer 330. Insome embodiments, the thickness of the interlayer for a single-clad foilmay be 1-25% of the thickness of the core layer 330. In someembodiments, the thickness of the interlayer for a double-clad foil maybe 2-50% of the thickness of the core layer.

In some embodiments, the thickness of the interlayer is less than thethickness of the core layer. In some embodiments, the total thickness ofa foil is greater than 25 μm. In other embodiments, the total thicknessof a foil is less than 1000 μm. The thicknesses of the core layer andinterlayers, as well as the ratio of the core layer thickness tointerlayer thickness, are variable and optimized to the specific bondingmethod in some embodiments.

In some embodiments, the specific composition of an interlayer isselected such that the interlayer material melts at a lower temperaturethan the core layer. In some embodiments, the interlayer material isselected to minimize the melting temperature. In some embodiments, themelting temperature of the interlayer material may be greater than 500°C. and less than 590° C. In some embodiments, the melting temperature ofthe interlayer material may be below 500° C. In a different subset ofthese embodiments, the melting temperature of the interlayer materialmay be below 490° C. In some embodiments, the ratio of interlayermaterial and core layer material and the compositions thereof areselected so the final mechanical properties of the object are that of adesired composition. In some embodiments where the interlayer componentis a small fraction of the total foil, the desired composition may bewithin the tolerances of the composition of the core material.

In some embodiments, the composition of the foils in a stack areselected so that, once heated, the finished object has a desiredcomposition. For example, if the finished object is to have a desiredcomposition matching a particular alloy, the individual sheets may eachhave a surplus or a deficiency of various elements but, when heated, thefinished object has a substantially homogenous composition matching thedesired composition.

For example, FIG. 4A depicts a foil 400 a in accordance with oneembodiment. Foil 400 a includes a single core layer 402 a that is cladon one side with an interlayer 404 a. FIG. 4B illustrates a foil 400 bin accordance with another embodiment. Foil 400 b includes a single corelayer 402 b that is cladded on both sides with an interlayer 404 b.

The core layers 402 a and 402 b may comprise a majority of aluminum ormagnesium. Additional alloying elements may be present such as, but notlimited to, copper, silicon, zinc, or other material as discussedpreviously.

The interlayers 404 a and 404 b may comprise some combination ofaluminum, copper, magnesium, silicon, and zinc, or other material asdiscussed previously. The interlayer(s) 404 a and 404 b mayalternatively comprise a uniform layer of any single element in theforegoing list.

In some embodiments, an interlayer comprises between 1-50% of the totalfoil thickness. In some embodiments, such as those in which theinterlayer comprises a single element, the interlayer may comprise athin layer of less than 5% of the total foil thickness.

The specific compositions of the core layer or interlayer(s) may matchthe composition of commercially available aluminum alloys. For example,a core layer may comprise 2024, 5182, 6061, or another alloy. Customalloys that largely match commercial alloy compositions but have eitherincreased or decreased concentrations of one or more elements present inthe interlayer(s) may also be employed. The interlayer(s) may comprise2024, 4004, 5182, 6061, 7075, or another commercial aluminum alloy.Interlayers may also comprise custom alloys that match commercial alloycompositions, but may also have increased or decreased concentrations ofone or more elements.

The compositions of the core layer and the interlayer(s) with respect toeach other may vary. For example, in some embodiments, an elementpresent in excess in an interlayer may be present in a lowerconcentration in the core layer to achieve a desired composition afterhomogenization.

Alternatively, an element present in excess in a core layer may bepresent in a lower concentration in the interlayer(s) to achieve adesired composition after homogenization. The relative thickness of thelayers may also be selected so that the average composition of the alloymatches 2024, 6061, 7075, or another desired composition.

As another example, the core layer(s) may comprise a magnesium alloywith a high melting point. The interlayer(s) may comprise a low meltingpoint magnesium alloy as well as custom alloys that have increased ordecreased concentrations of the alloying elements. In some embodiments,the interlayer(s) may comprise an element that depresses the meltingpoint of magnesium.

In operation, a user or system may provide a part to a heatingenvironment such as a furnace. The furnace may apply heat to the part(s)to raise the temperature of the part(s) and maintain the temperature ofthe part(s) at a certain temperature or range of temperatures for aperiod of time. Specifically, the techniques in accordance with theembodiments herein may involve a bonding phase in which layers areheated and bonded together, and then a homogenization phase in which thebonded layers are heated to produce a homogenized product. Thehomogenized product may then be quenched.

In some embodiments, the bonded parts may be transferred to a separatefurnace processing unit that performs the homogenization phase. Theparts may be moved with a supporting structure, for example. In otherembodiments, a chamber may protect the parts during movement to protectthe surface from oxidation. In some embodiments, the chamber may beunder vacuum, or be a shield gas chamber with an inert or non-oxidativegas present around the part. In some embodiments, these steps mayfurther include a polishing step in which parts may be polished orotherwise modified prior to or after the homogenization process.

During the heating phase, the furnace may apply heat to the part(s) toincrease its temperature up to the processing temperature. That is, heatmay be applied to the part until the part's temperature reaches theprocessing temperature.

In some embodiments, the processing temperature is less than the solidustemperature of an interlayer and a core layer. For example, a furnacemay be configured to set the processing temperature to be 5° C. to 100°C. below the solidus temperature of the interlayer.

In some embodiments, the part(s) may be in a heated press during thehomogenization process to increase or improve heat transfer to the part.Well-controlled heat transfer may allow the part to be heated moreevenly and consistently during the processing phase, allowing finecontrol over the rate at which elements diffuse in the part without thepart melting. This improves the rate of diffusion and reduces the chanceof defects forming in the part.

FIG. 4C illustrates a foil or part 406 that is manufactured by stackingfoils such as the foils 400 a or 400 b. For example, part 406 is seen asincluding a plurality of core layers 402 c and a plurality ofinterlayers 404 c.

During the homogenization process, a foil such as foils 400 a—c is heldat the processing temperature for a period of time to allow the elementsin the interlayer(s) and core layer(s) to interdiffuse, thereby forminga roughly uniform composition in both regions. This interdiffusionprocess involves two concurrent phenomena. That is, elements that arepresent in the interlayer(s) diffuse into the core layer region, andelements that are present in the core layer diffuse into the interlayerregion. As the thickness of the core layer may be at least a multiplegreater than that of the interlayer(s), the slowest diffusing element isa component present in at least one of the core layer and interlayerthat diffuses into the complementary layer.

Additionally, elements with a lower diffusion coefficient diffuse moreslowly at the same concentration gradient, temperature, and at otherenvironmental conditions than elements with a higher diffusioncoefficient. The slowest diffusing element is therefore the element withthe lowest diffusion coefficient. The foil may be considered homogenizedonce the slowest diffusing element is present in both the regionspreviously occupied by the core layer and interlayer(s), and the peakcomposition of the slowest diffusing element is within the standardtolerances for alloy composition in published standards, such asspecified TEAL sheets.

FIG. 4D illustrates a part 408 produced from a homogenization process inaccordance with one embodiment. As seen in FIG. 4D, the part 408 has atleast a portion that is fully homogenized and uniform in composition.

FIG. 5 illustrates a concentration profile 500 of an interfaceencompassing interlayer 502 and bordering two core layers 504 as afunction of time during the homogenization process. In this example,there is initially (i.e., before a homogenization process begins) analloying element that is present in the interlayer 502 but is notpresent in either of the core layers 504.

Series 506 represents the initial concentration of this alloying elementbefore the homogenization process begins. As seen in FIG. 5 , theconcentration of this alloying element in the interlayer 502 is high,but is zero in the core layers 504. That is, the composition of the corelayers 504 does not include the alloying element before thehomogenization process begins.

The three progressive series 508, 510, and 512 represent theconcentration of the alloying element at different times throughout thehomogenization process. Series 508 represents the alloying elementconcentration at time t1, series 510 represents the alloying elementconcentration at time t2, and series 512 represents the alloying elementconcentration at time t3, where t1<t2<t3. From t1−t3, the composition ofalloying element in interlayer 502 decreases as it is being diffused outof the area previously occupied by the interlayer 502. As this occurs,the composition of the alloying element in the core layers 504increases. Series 514 represents the concentration of the alloyingelement at the end of the homogenization process. As seen in profile500, the concentration of the alloying element has decreased in theinterlayer 502 and has increased in the core layers 504.

FIG. 6 illustrates an operating profile 600 for a homogenization processas a function of time in accordance with one embodiment. Thehomogenization process associated with the profile 600 of FIG. 6 may besimilar to the process described in conjunction with FIG. 5 , forexample.

The temperature 602 is initially at room or ambient temperature 604before the homogenization process begins. The temperature 602 may beheated to a temperature that is below the interlayer solidus temperature606. The interlayer solidus temperature 606 is less than the core layersolidus temperature 608.

The time required for the homogenization process is partly determined bythe thicknesses of the core layer and the interlayer. For example, thetime required for the homogenization process scales with the thicknessof the layers. Specifically, foils with thinner interlayers require lesstime to homogenize.

Similarly, the rate at which diffusing elements move is increased withincreased temperature. The time required for the homogenization processis therefore also a function of temperature and is reduced as theprocessing temperature is increased.

After some period of time that is sufficient to facilitate thehomogenization process, the temperature 602 may be reduced back to theroom or ambient temperature 604. The cooling phase may involve quenchingthe part in water, oil, or another fluid; using fans or otherwise byblowing air to cool the part, cooling naturally, or the like.

FIG. 7 depicts a flowchart of a method 700 for the manufacturing of anobject in accordance with one embodiment. Homogenized parts producedfrom two or more different component alloys may exhibit mechanicalproperties that are superior to any of the constituent alloys. In someinstances, the composition of the alloys that are selected for thecomponent layers may have weaker mechanical properties than the finalhomogenized part.

For example, the core layer and the interlayer(s) may alternativelycomprise a greater fraction of magnesium and silicon than thestoichiometric ratio of 2:1. This ratio would typically produce a weak,pliable material. However, the overall fractions of magnesium andsilicon are present in a ratio such that the homogenized part is a highstrength, hardened 6000-series alloy with a magnesium-to-silicon ratioto meet a desired alloy composition. This allows alloys to have theirprocessing conditions such as melting temperatures fine-tuned by theselective presence of magnesium and silicon without the negativeconsequences of an excess of one of those elements in the final,homogenized part.

Step 702 involves receiving a desired alloy composition for the object.The desired alloy composition may be a copper-rich aluminum alloy in the2000 series, silicon-rich aluminum alloy in the 4000 series, amagnesium-rich aluminum alloy in the 5000 series, a magnesium andsilicon-rich aluminum alloy in the 6000 series, a zinc-rich aluminumalloy in the 7000 series, etc.

Step 704 involves depositing a plurality of foils in a stack to form theobject. The type(s) of foils deposited in a stack as part of step 704may depend on the desired alloy composition specified in step 702.

For example, if the desired alloy composition is an aluminum alloy inthe 6000 series, then core layers of 6000-series alloys and interlayersof 2000-series alloys may be employed. In this case, the copper from thecopper-rich 2000-series interlayer would diffuse into the core layer ofthe 6000-series alloy, producing a low-copper 6000-series alloy such as6061, which is a high-strength machining alloy.

If the desired alloy composition is a magnesium-rich aluminum alloy inthe 5000 series, then core layers of 1000-, 3000-, or 1000-series alloysand interlayers of 5000 series alloys may be employed. If the desiredalloy composition is a silicon-rich aluminum alloy in the 4000 series,then core layers of 6000-series alloys and interlayers of 4000-seriesalloys may be employed. If the desired alloy composition is a zinc-richaluminum alloy in the 7000 series, core layers of at least one of 2000-,5000-, 6000-, or 7000-series alloys and interlayers of 7000-seriesalloys may be employed.

In some embodiments, where the homogenized part is an aluminum alloy ofthe X000 series, both the interlayer and core layers may be alloys ofthe same X000 series. In other embodiments, where the homogenized partis an aluminum alloy of the X000 series, both the interlayer and corelayer may be custom alloys that match the composition of the X000series, except one of the core layer or interlayer has an excess of atleast one element, and the complementary alloy has a deficit of at leastone of the same element.

In some embodiments, the composition of individual foil layers in thestack can be selected such that, when diffused using the foregoingprocesses, the result is an object having a homogenous composition thatmatches a desired composition that is non-identical to that of theconstituent foils. The following tables identify several alloys as wellas the constituent foils that can be used to achieve those alloys.

TABLE 1 Desired alloy is a 6000-series aluminum alloy (all compositionsin wt %) Si Fe Cu Mn Mg Cr Zn Ti Core 0.5- <0.3 <0.1 <0.1 0.9- 0.04-<0.25 <0.15 0.7 1.1 0.35 Clad 0.8- <0.3 1.5-2.7 <0.1 0.4- 0.04- <0.25<0.15 1.6 1.1 0.35

TABLE 2 Desired alloy is a 6000-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core 0.2- <0.3 0.15-0.4 <0.1 0.9-0.04- <0.25 <0.15 0.3 1.1 0.35 Clad 1.3- <0.3 0.15-0.4 <0.1 0.9- 0.04-<0.25 <0.15 1.7 1.1 0.35

TABLE 3 Desired alloy is a 6000-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core 0.1- <0.35 <0.1 <0.1 0.25 <0.1<0.1 <0.1 0.2 -0.45 Clad 0.8- <0.35 <0.1 <0.1 1.0- <0.1 <0.1 <0.1 1.01.3

TABLE 4 Desired alloy is a 6000-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core 0.5- <0.5 <0.1 0.4- 0.7- <0.25<0.2 <0.1 0.7 1.0 0.9 Clad 1.3- <0.5 <0.1 0.4- 0.5- <0.25 <0.2 <0.1 1.51.0 0.7

TABLE 5 Desired alloy is a 2000-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core 0- <0.3 3.5- 0.3- 1.2- <0.1 <0.25<0.15 0.25 3.8 0.9 1.8 Clad 0.4- <0.3 4.8- 0.3- 1.2- <0.1 <0.25 <0.150.7 5.2 0.9 1.8

TABLE 6 Desired alloy is a 2000-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core 0.1- <0.7 3.75- 0.4- 0.2- <0.1<0.25 <0.15 0.6 4.25 1.2 0.8 Clad 1.0- <0.7 4.2- 0.4- 0.8- <0.1 <0.25<0.15 1.8 5.5 1.2 1.4

TABLE 7 Desired alloy is a 7000-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core <0.1 <0.5 1.0- <0.3 1.9- 0.18-5.0- <0.15 1.3 2.1 0.28 5.4 Clad 0.5- <0.5 2.0- <0.3 2.8- 0.18- 5.8-<0.15 0.7 2.4 3.0 0.28 6.2

TABLE 8 Desired alloy is a 7000-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core <0.12 <0.15 1.6- <0.1 1.5- <0.045.4- <0.15 2.0 1.9 5.7 Clad <0.12 <0.15 3.0- <0.1 2.8- <0.04 6.5- <0.153.2 3.2 7.0

TABLE 9 Desired alloy is a 7000-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core <0.06 <0.08 1.0- <0.4 0.9- <0.046.6- <0.06 1.6 1.3 7.0 Clad <0.06 <0.08 1.8- <0.4 1.4- <0.04 8.0- <0.062.2 2.0 8.6

TABLE 10 Desired alloy is a 300-series aluminum alloy (all compositionsin wt. %) Si Fe Cu Mn Mg Cr Zn Ti Core 7.0- <1.3 2.6- <0.5 <0.1 — 1.0- —7.5 3.0 1.5 Clad 10.0- <1.3 4.25- <0.5 <0.1 — 2.0- — 11.0 4.75 2.5

Each table specifies the different compositions of the core layer andthe cladding layer (i.e., an interlayer), while the table labelspecifies the desired alloy series. The number entries correspond to theweight fractions of each of the major alloying elements, with thebalance being aluminum (Al). These above compositions are merelyexemplary and other compositions may be achieved in accordance with theembodiments herein.

The foils may be clad on one or both sides, and the total thickness ofthe foil may be between 25 μm and 1,000 μm. The core layer thickness istypically greater than the interlayer thickness. In some embodiments thefoils are “all core” or “all clad” for each example. In theseembodiments, the foils may be alternated to create the same striatedlayer structure of alternating core and clad layers as can be generatedwith a stack of cladded foils.

Step 706 involves applying heat to the stack at a first temperature tobond the plurality of foils to each other. The stack may comprise a foilof a plurality of layers. Each layer may comprise, for example, analuminum alloy, a magnesium alloy, or a titanium alloy. The alloyingmaterial may be aluminum, chromium, copper, lithium, magnesium,manganese, titanium, nickel, silicon, or zinc. The first temperaturethat is required to bond the foils together may depend on thematerial(s) used.

Step 708 involves applying heat to the stack at a second temperature tohomogenize the composition of the stack. As discussed previously, thestack (e.g., a foil) may be heated to achieve a desired level ofinterdiffusion. In some embodiments, the second temperature is less thanthe melting points of the plurality of foils. In some embodiments, thesecond temperature may be approximately the solidus temperature of theplurality of foils or of the desired alloy composition. In someembodiments, the second temperature may be the same as the firsttemperature.

Step 710 is optional and involves quenching the stack afterhomogenization. This quenching step may occur in the same processingunit in which the homogenization step occurs or may occur in a locationother than the processing unit in which the homogenization step occurs.The optional quenching step may be employed depending on the desiredalloy properties.

FIG. 8 depicts an additive manufacturing system 800 comprising twoplates 805′, 805″ (collectively “805”) configured to apply at least oneof heat and pressure to a layer stack 815 to join foils 810 inaccordance with one embodiment. Some embodiments may use at least onebonding method to join at least two foils 810 within a layer stack 815.

In some embodiments, the platens 805 may be at least one of pressurizedor heated plates. In some embodiments, the platens 805 may be configuredto apply at least one of heat or pressure to opposite sides of the layerstack 815. In some embodiments, applying the at least one of heat orpressure increases the temperature of the layer stack 815 to atemperature lower than the melting temperature of the core layer of thefoils 810, such that the at least one of heat or pressure bonds thefirst foil to the second foil in the layer stack 815.

In some embodiments, to bond the object region 820, the plates 805 mayapply even pressure to the layer stack 815. In some embodiments, thelayer stack 815 may comprise a full encasing of the object region 820.The full encasing may comprise at least two support regions 825, 830,such that the object region 820 is fully enclosed in the support regions825, 830.

In some embodiments, the support regions 825, 830 are configured toconduct at least one of heat or pressure through the layer stack 815from the plates 805. This conduction of heat or pressure promotesbonding of the foils 810 to form a bonded object region 820. In someembodiments, the plates 805 apply at least one of heat or pressure tothe support regions 825, 830, which in turn conduct the at least one ofheat or pressure to the object region 820. In some embodiments, thesupport regions 825, 830 may have flat surfaces, such that the plates805 may evenly apply at least one of pressure or heat across the entiresurface. In some embodiments, the support region is a singular supportregion surrounding the object region 820 and may be used to create anegative of an object. In some embodiments, the bonding process of theobject region 820 may occur under oxidizing atmospheres, such as air. Insome embodiments, the bonding process of the foils 810 may be enclosedin a vacuum or inert gas chamber.

In some embodiments, the system may employ at least one of diffusionbonding, transient liquid diffusion bonding, and/or brazing. In someembodiments, the alloy composition and processing conditions areoptimized for efficient diffusion bonding.

FIG. 9 schematically shows a method 900 for the additive manufacturingof an object through diffusion bonding in accordance with oneembodiment. The method 900 comprises applying heat to the stack of foilsto bring the foils to a bonding temperature (Step 905). In someembodiments, bonding temperature may be less than the meltingtemperature of the core layer of the foils and high enough to promotediffusion and bonding between adjacent foils. In some embodiments, thebonding temperature may be less than the temperature of the interlayerof the foils. In some embodiments, at least one plate may apply heat tothe foils.

In some embodiments, the stack of foils may be brought up to bondingtemperature and optional pressure (Step 915) and held at the bondingtemperature and optional pressure (Step 925) until the elements fromadjacent core layers diffuse into each other, joining the stack of foilsinto an object region (Step 930).

In some embodiments, the method may comprise a sequential diffusionbonding process. In a sequential diffusion bonding process, the methodmay comprise adding a foil to an object or part of an object at thebonding temperature (Step 920). In some embodiments, the bondingtemperature may be less than the melting temperature of the core layermaterial. Alternatively, the foil may be added to a cold foil stack andthe stack with the additional foil may be brought to bondingtemperature. In some embodiments, a foil is added to an already heatedstack and the pressure is applied to the stack. In some embodiments,after the pressure is applied, the pressure is relaxed to add anotherfoil (Step 920).

In some embodiments, the temperature may promote diffusion and bondingbetween the elements of the core layer of the added foil and the object,causing the bonding process to occur.

In some embodiments, at least one of the object or a component thereofmay serve as a heat sink. In some embodiments, the heat sink maygenerate a temperature gradient across the object for the purpose ofselectively promoting diffusion bonding in one sub-region of the object.In some embodiments, the diffusion process may be repeated until theobject is completed.

FIG. 10 schematically shows a method 1000 for additive manufacturing ofan object through transient liquid phase (TLP) diffusion bonding inaccordance with one embodiment. Some embodiments may optimize the alloycomposition and processing conditions for efficient bonding throughtransient liquid phase (TLP) diffusion bonding under an oxidizing ornon-oxidizing atmosphere, or a vacuum.

In some embodiments, the core material is aluminum or an aluminum alloy.In some embodiments, the core material may comprise at least one ofaluminum, magnesium, titanium, copper, silicon, or zinc. The alloyingelements may comprise at least one of magnesium or zinc. In someembodiments, the cladding interlayer may comprise at least one of analuminum-magnesium alloy, a magnesium-zinc alloy, an alloy of at leasttwo of aluminum, copper, magnesium, silicon, or zinc, or any combinationthereof. In some embodiments, at least one of these interlayer alloyingelements may serve as an oxide getter, preferentially binding to oxygenat a greater rate than aluminum.

In some embodiments, the aluminum alloy foil may comprise between 20%and 100% aluminum. In some embodiments, the aluminum alloy foil maycomprise at least one of Sb, Ba, Be, Bi, B, Cd, Ca, C, Cr, Co, Cu, Ga,Fe, Pb, Li, Mg, Mn, Ni, O, P, K, Sc, Si, Ag, Na, Sr, Sn, Ti, V, Zn, orZr. In some embodiments, the aluminum alloy foil may comprise more than50% Cu. In some embodiments, the aluminum alloy foil may comprise morethan 40% Fe. In some embodiments, the aluminum alloy foil may comprisemore than 40% Mg. In some embodiments, the aluminum alloy foil maycomprise more than 40% Ni. In some embodiments, the aluminum alloy foilmay comprise more than 40% Zn. In some embodiments, the aluminum alloyfoil may comprise more than 60% Si.

In some embodiments, the magnesium alloy foil may comprise between 45%and 100% magnesium. In some embodiments, the magnesium alloy foil maycomprise at least one of Al, Be, Ca, Ch, Cu, Gd, Fe, Li, Mn, Nd, Ni, Si,Ag, Th, Y, Zn, Zr, or rare earth metals. In some embodiments, themagnesium alloy foil may comprise more than 40% Al.

In some embodiments, the titanium alloy foil may comprise between 70%and 100% titanium. In some embodiments, the titanium alloy foil maycomprise at least one of Al, B, C, Cr, Cu, H, Fe, Mn, Mo, Ni, Nb, N, O,Pd, Si, S, Ta, Sn, V, Y, or Zr.

In some embodiments, the melting temperature of the interlayer may be atleast 10° C. less than the melting temperature of the core layer. Themelting temperature of the interlayer may be minimized to reduce energycost and machine complexity of processing. In some embodiments, themelting temperature of the interlayer may be below 500° C.

In some embodiments, the overall foil thickness is generally between 25μm and 1000 μm. Each interlayer may be up to 50% of the thickness of thecore material and may be between 1 μm and 50 μm thick. The interlayermaterial may be deposited on either one or both sides of the corematerial to form a single foil.

In some embodiments, methods may use diffusing elements comprising atleast one of Cu, Mg, Zn, or Si. In some embodiments, the interlayer maycomprise at least 0.2% Cu. In some embodiments, the diffusing elementmay comprise at least 1% Cu. In some embodiments, the diffusing elementmay comprise at least 2% Cu. In some embodiments, the diffusing elementmay comprise a maximum of 4% Cu. In some embodiments, the diffusingelement may comprise a maximum of 5% Cu. In some embodiments, thediffusing element may comprise a maximum of 6% Cu. In some embodiments,the diffusing element may comprise a maximum of 6.3% Cu.

In some embodiments, the method comprises bringing the stack of foils upto bonding temperature (Step 1005), which is greater than the meltingtemperature of the interlayer but less than the melting temperature ofthe core layer of the constituent foils.

In some embodiments, the method may comprise compressing the stack offoils by applying pressure (Step 1010). In some embodiments, thepressure may be on the order of 0.1-100 MPa.

In some embodiments, applying at least one of temperature or pressuremay cause interlayer to melt, increasing the rate of diffusion of theelements of the core layer into the interlayer, and the elements of theinterlayer into the core layer (Step 1015). In some embodiments, appliedpressure may promote mixing of the elements between the core layers andinterlayers of adjacent foils.

In some embodiments, as the elements of the interlayers and core layerinterdiffuse, the average composition of the stacked foils changes toresemble the final average composition of the object, and the meltingtemperature increases corresponding to the composition change. In someembodiments, new bonds are formed between metallic components.

In some embodiments, this process can be accomplished sequentially. In asequential process, a foil may be added to a part at the bondingtemperature, which is greater than the melting temperature of theinterlayer material, or a new foil may be added to a cold stack which isthen brought up to bonding temperature. In some embodiments, theinterlayer of the added foil may melt (Step 1015) to continue thebonding process.

In some embodiments, previously deposited layers are not affected bythis process, as their constituent interlayers have alreadyinter-diffused with the core layers, and bonded so that the part willnot melt at the applied bonding temperature.

FIG. 11 schematically shows a method 1100 for additive manufacturing ofan object through brazing in accordance with one embodiment. In someembodiments, brazing is used to optimize the alloy composition andprocessing conditions for bonding.

In some embodiments, the method comprises depositing a first foil (Step1105). In some embodiments, the first foil may be deposited onto a printbed. In some embodiments, the first foil may be deposited onto a foil.In some embodiments, the method further comprises depositing a secondfoil (Step 1115). In some embodiments, the foils may comprise at leastone interlayer and at least one core layer.

In some embodiments, the foils may be brought up to the bondingtemperature (Step 1120). In some embodiments, bonding temperature isgreater than the melting temperature of the interlayer but less than themelting temperature of the core layer of the foils.

In some embodiments, the foils may be held at this bonding temperaturefor a fixed period of time (Step 1125). In some embodiments, holding thefoils at a bonding temperature may allow the interlayers to melt, whichincreases the rate of diffusion of the elements of the core layer intothe interlayer, and correspondingly the elements of the interlayer intothe core layer.

This process causes the formation of metallic bonds between theadjacently stacked foils, forming an object (Step 1130).

In some embodiments, the brazing process may be accomplishedsequentially. In a sequential brazing process, a foil may be added to asub-assembly or object comprising several bonded foils. In someembodiments, an additional liquid flux may be applied to the void spacebetween the added foil and the object.

In some embodiments, the added foil and the part may be brought up tothe bonding temperature, which is greater than the melting temperatureof the interlayer of the added foil but less than the meltingtemperature of the core layer of the added foil, as well as the lessthan the melting temperature of the alloy that makes up the part (Step1120).

In some embodiments, the added foil and the part may be held at thisbonding temperature for a fixed period of time (Step 1125), which meltsthe interlayer of the added foil and the bonding process described aboveoccurs.

In some embodiments, the previously deposited layers may not be affectedby this process, as their constituent interlayers have already melted,inter-diffused with the core layers, and bonded so that the object willnot melt at the applied bonding temperature.

In some embodiments the alloy compositions of the core layer andinterlayer could be used in other form factors, such as core-structuredpowders or core-structured wires, or a combination of two powdercompositions. These could then be bonded and when diffused using theforegoing processes, the result is an object having a homogenouscomposition that matches a desired composition that is non-identical tothat of the constituent inputs.

The methods, systems, and devices discussed above are examples. Variousconfigurations may omit, substitute, or add various procedures orcomponents as appropriate. For instance, in alternative configurations,the methods may be performed in an order different from that described,and that various steps may be added, omitted, or combined. Also,features described with respect to certain configurations may becombined in various other configurations. Different aspects and elementsof the configurations may be combined in a similar manner. Also,technology evolves and, thus, many of the elements are examples and donot limit the scope of the disclosure or claims.

Embodiments of the present disclosure, for example, are described abovewith reference to block diagrams and/or operational illustrations ofmethods, systems, and computer program products according to embodimentsof the present disclosure. The functions/acts noted in the blocks mayoccur out of the order as shown in any flowchart. For example, twoblocks shown in succession may in fact be executed substantiallyconcurrent or the blocks may sometimes be executed in the reverse order,depending upon the functionality/acts involved. Additionally, oralternatively, not all of the blocks shown in any flowchart need to beperformed and/or executed. For example, if a given flowchart has fiveblocks containing functions/acts, it may be the case that only three ofthe five blocks are performed and/or executed. In this example, any ofthe three of the five blocks may be performed and/or executed.

A statement that a value exceeds (or is more than) a first thresholdvalue is equivalent to a statement that the value meets or exceeds asecond threshold value that is slightly greater than the first thresholdvalue, e.g., the second threshold value being one value higher than thefirst threshold value in the resolution of a relevant system. Astatement that a value is less than (or is within) a first thresholdvalue is equivalent to a statement that the value is less than or equalto a second threshold value that is slightly lower than the firstthreshold value, e.g., the second threshold value being one value lowerthan the first threshold value in the resolution of the relevant system.

Specific details are given in the description to provide a thoroughunderstanding of example configurations (including implementations).However, configurations may be practiced without these specific details.For example, well-known circuits, processes, algorithms, structures, andtechniques have been shown without unnecessary detail in order to avoidobscuring the configurations. This description provides exampleconfigurations only, and does not limit the scope, applicability, orconfigurations of the claims. Rather, the preceding description of theconfigurations will provide those skilled in the art with an enablingdescription for implementing described techniques. Various changes maybe made in the function and arrangement of elements without departingfrom the spirit or scope of the disclosure.

What is claimed is:
 1. A cladded foil comprising: a core comprising abalance of Al and between 0.1-0.2 wt. % Si, and between 0.25-0.45 wt. %Mg; and a cladding comprising a balance of Al and between 0.8-1.0 wt. %Si, and between 1.0-1.3 wt. % Mg.
 2. The cladded foil of claim 1, withthe trace elements in the core and clad compositions comprising between0-0.35 wt. % Fe, between 0-0.1 wt. % Cu, between 0-0.1 wt. % Mn, between0-0.1 wt. % Cr, between 0-0.1 wt. % Zn, and between 0-0.1 wt. % Ti, withany other elements less than 0.05 wt. % and the total of all otherelements less than 0.15 wt. %.
 3. The cladded foil of claim 1, whereineach foil is between 25 um and 1000 um in thickness.
 4. The cladded foilof claim 1, wherein the core is a first layer of the foil and thecladding is a second layer of the foil.
 5. The cladded foil of claim 1,wherein a first layer forms a first cladding of the foil, a second layerforms the core of the foil, and a third layer forms a second cladding ofthe foil.
 6. The cladded foil of claim 1, wherein the cladding isbetween 10% and 50% of the total thickness of the cladded foil.